A friend recently told me that cats must have beef in their diet, otherwise they'll go blind.

Is this true? Or, is she confusing it with dogs ?

Answer:

No, this is not true and neither does it apply to dogs. She most likely is referring to an amino acid (building block of a protein) called TAURINE which is a very specific requirement for cats which if they do not get, can cause among other things, blindness. This is quite cute since she must have understood that Taurine sounds like taurus which means bull in Latin and this may translate to beef. Rest assured most good quality cat foods have taurine supplement in them.